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Results for “PALMITIC ACID”

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At least 199 records · Page 11Linked to original sources

PubMed1999

Effect of glucose load on the transport kinetics of palmitic acid in the human placenta: an in vitro study.

1. A paucity of data relating to free fatty acid (FFA) transport in the human placenta in non-steady state conditions prompted us to undertake the present study. 2. The transport kinetics of palmitic acid in non-steady state conditions have been investigated in vitro using human perfused placental lobules. The effects of varying glucose concentrations on maternal-foetal transport of the FFA were also investigated to mimic the hyperglycaemic states of human diabetic pregnancies. 3. National Cancer Tissue Culture medium diluted with Earle's buffered salt solution was used as the perfusate. [14C]-Palmitic acid, along with tritiated water as a reference, was injected as a bolus into the maternal arterial perfusate and perfusate samples were collected from the venous outflow for a period of 5 min. 4. The transport fraction (TF) of palmitic acid, expressed as percentage of the injected bolus, averaged 3.45 +/- 0.15% in five perfusions, representing 9.2 +/- 1.3% of the corresponding reference marker TF. Kinetic parameters, as well as TF indices of palmitic acid expressed in relation to the reference substance, did not differ significantly between perfusions with a physiological glucose load and those with hyperglycaemic concentrations of glucose of 27.8 and 55.6 mmol/L. 5. The present study shows that hyperglycaemia per se does not significantly alter palmitic acid transport kinetics in vitro in the human perfused placental lobule.

Female↗

PubMed2001

Palmitic acid uptake by the rat soleus muscle in vitro.

Abstract: The rate of fatty acid uptake, oxidation, and deposition in skeletal muscles in relation to total and unbound to albumin fatty acids concentration in the medium were investigated in the incubated rat soleus muscle. An immunohistochemical technique was applied to demonstrate whether the albumin-bound fatty acid complex from the medium penetrates well within all areas of the muscle strips. It was found that the percentage of incorporation of palmitic acid into intramuscular lipids was fairly constant, independently of the fatty acid concentration in the medium, and amounted to 63-72% for triacylglycerols, 7-12% for diacylglycerols-monoacylglycerols, and 19-26% for phospholipids. Both palmitic acid incorporation into the muscle triacylglycerol stores and its oxidation to CO2 closely correlated with an increase in both total and unbound to albumin fatty acid concentrations in the incubation medium. Under conditions of increased total but constant unbound to albumin palmitic acid concentrations, the incorporation of palmitic acid into triacylglycerols and its oxidation to CO2 were also increased, but to a lower extent. This supports the hypothesis that the cellular fatty acid metabolism depends not only on the availability of fatty acids unbound to albumin, but also on the availability of fatty acids complexed to albumin.

Animals↗

PubMed1985

In vivo acylation of Dictyostelium actin with palmitic acid.

Cells of Dictyostelium discoideum were incubated with [H]palmitic acid during development, and recovery of the fatty acid label in soluble and membrane-associated proteins was investigated. One of the major labeled proteins was found exclusively in the soluble fraction. This protein, with an apparent mol. wt. of 44 kd, was identified as actin based on its labeling with a monoclonal anti-actin antibody, its coincidence with the major [S]methionine-labeled protein after two-dimensional electrophoresis and its binding to a DNase I affinity column. The H-label was resistant to chloroform-methanol extraction and boiling in SDS-containing buffer. After partial purification by preparative SDS-polyacrylamide gel electrophoresis, the 44-kd protein was treated with KOH, the fatty acids released were derivatized to methyl esters and palmitic acid methylester was identified by gas-liquid chromatography.

Journal Article↗

PubMed1988

Oxidation of palmitic acid by Mycobacterium leprae in an axenic medium.

The ability of Mycobacterium leprae to oxidize palmitic acid during incubation in an axenic medium was studied. By using a Buddemeyer-type detection system, partially purified nude-mouse-derived M. leprae was found to produce 14CO2 from 14C-labeled palmitic acid in a linear fashion for at least 1 week. Procedures known to remove residual host tissue did not diminish the rate of 14CO2 evolution, indicating that bacterial metabolism was being measured. Palmitate oxidation was temperature sensitive, with an apparent optimum of 33 degrees C, but pH insensitive. Bacilli exposed to a variety of antileprosy drugs for 1 or 2 weeks displayed significantly reduced rates of 14CO2 evolution upon subsequent addition of 14C-labeled palmitic acid. This activity could be readily detected with 10(6) bacilli, thus indicating its potential for use in clinical susceptibility testing.

Carbon Dioxide↗

PubMed1991

The role of palmitic acid in pulmonary surfactant: enhancement of surface activity and prevention of inhibition by blood proteins.

The surface activity of two surfactant preparations, Lipid Extract Surfactant (LES) and Survanta, was examined during adsorption and dynamic compression using a pulsating bubble surfactometer. At low surfactant phospholipid concentrations (1-2.5 mg/ml), Survanta reduces surface tension at minimum bubble radius faster than LES: however, with continued pulsation LES obtains a lower surface tension. Addition of surfactant-associated protein A (SP-A) to LES significantly reduces the time required to reduce surface tension. Survanta is completely unresponsive to the addition of SP-A in that no further reduction of surface tension is observed. Addition of various blood components has been previously shown to inactivate surfactants in vitro. Addition of fibrinogen to Survanta causes an increase in surface tension when measured in the absence of calcium. When assayed in the presence of calcium, inhibition by fibrinogen is not observed possibly due to aggregation of this protein. Albumin and alpha-globulin strongly inhibit Survanta at physiological serum concentrations both in the presence and absence of calcium. The surface activity of Survanta is also inhibited by lysophosphatidylcholine (lyso-PC). The role of palmitic acid in the surface activity of pulmonary surfactant was examined by adding palmitic acid to LES. At low phospholipid concentrations addition of palmitic acid (10% w/w of the surfactant phospholipid) greatly enhances the surface activity of LES. Maximal enhancement of surface activity and adsorption was observed at or above 7.5% added palmitic acid (w/w of surfactant lipid). LES supplemented with palmitic acid is more resistant to inhibition by fibrinogen, albumin, alpha-globulin and lyso-PC than LES alone, however, the counteraction of blood protein inhibition is not as pronounced as that observed with SP-A.

Albumins↗

PubMed1991

Trypanosoma cruzi: incorporation of [3H]-palmitic acid and [3H]-galactose into components shed by trypomastigotes.

Trypomastigotes were metabolically labeled with [3H]-palmitic acid or [3H]-galactose and labeled components were detected in the culture medium. Thin layer chromatography of the shed material showed several lipids in the [3H]-palmitic acid labeled sample while the sugar was mainly incorporated into macromolecules. The material incorporated with the lipidic precursor was fractionated by DEAE-Sephadex (acetate form) and the amount of radioactivity was ten times higher in the acidic lipids than in the neutral lipids. When acidic lipids were further separated by Unisil, 73% of the radioactivity was recovered in the less polar fraction. Different patterns were obtained on comparison of the shed components with the lipids remaining in the parasite.

Animals↗

PubMed1994

[Interaction of palmitic acid with the ADP/ATP antiporter, reconstituted in liposomes].

Reconstituted adenine nucleotide transport has been studied in proteoliposomes with the ADP/ATP antiporter and bacteriorhodopsin as the membrane potential generator. The ADP(out)/ATP(in) exchange rate in the model system decreased after illumination of the proteoliposomes. This effect was reversed by both protonophore FCCP and palmitic acid. The data obtained are analysed in terms of the electrogeneity of the nucleotide transport by the antiporter. It is suggested that palmitic acid increases the conductivity of the proteoliposome membrane. The membrane conductivity of bacteriorhodopsin proteoliposomes (without the ADP/ATP antiporter) is unaffected by palmitic acid. Seemingly, the ADP/ATP antiporter mediated increase of the proteoliposomal membrane conductivity is induced by fatty acids. Stimulation of the adenine nucleotide transport by fatty acids was also observed in the reconstituted system, when the membrane potential was absent. Besides palmitic acid, other anionic uncouplers, DNP and FCCP, produce a similar, however, less pronounced effect. Gramicidin D is without effect. It is concluded that the observed stimulating effect is due to the anionic uncoupler interaction with the ADP/ATP antiporter rather than to the membrane proton conductivity increase.

Bacteriorhodopsins↗

PubMed1974

Effect of palmitic acid utilization on cell division in Mycobacterium avium.

Mycobacterium avium, a facultative pathogen for humans, undergoes a life cycle in which selected small cells elongate and then fragment to form coccobacilli. M. avium cells of uniform size were selected by membrane filtration and tested for growth and division in the presence or absence of palmitic acid. Growth was measured by increased cellular protein, and cell division was determined by increased colony-forming units on agar or, electronically, by increased numbers of particles. Both growth and division rates of M. avium were found to be dependent upon the initial concentration of palmitic acid presented to the cells. The division constant varied from 0.05 to 0.13 when the concentration of palmitic acid ranged from 0 to 175 nmol/ml of medium. With [(14)C]palmitic acid as a tracer, it was found that rapid cell division began upon cessation of fatty acid uptake. During division, new lipid materials were released which contained (14)C derived from [(14)C]palmitic acid. Limited cell division and no fragmentation occurred in fatty acid-starved cultures. During fatty acid starvation, the transparent colony form, considered a pathogen, underwent a transition to the colony form considered a nonpathogen. The possible relationships between the organism's dependence on fatty acid and its ability to infect humans are discussed.

Carbon Radioisotopes↗

PubMed2001

Glucose and palmitic acid induce degeneration of myofibrils and modulate apoptosis in rat adult cardiomyocytes.

Several studies support the concept of a diabetic cardiomyopathy in the absence of discernible coronary artery disease, although its mechanism remains poorly understood. We investigated the role of glucose and palmitic acid on cardiomyocyte apoptosis and on the organization of the contractile apparatus. Exposure of adult rat cardiomyocytes for 18 h to palmitic acid (0.25 and 0.5 mmol/l) resulted in a significant increase of apoptotic cells, whereas increasing glucose concentration to 33.3 mmol/l for up to 8 days had no influence on the apoptosis rate. However, both palmitic acid and elevated glucose concentration alone or in combination had a dramatic destructive effect on the myofibrillar apparatus. The membrane-permeable C2-ceramide but not the metabolically inactive C2-dihydroceramide enhanced apoptosis of cardiomyocytes by 50%, accompanied by detrimental effects on the myofibrils. The palmitic acid-induced effects were impaired by fumonisin B1, an inhibitor of ceramide synthase. Sphingomyelinase, which activates the catabolic pathway of ceramide by metabolizing sphingomyeline to ceramide, did not adversely affect cardiomyocytes. Palmitic acid-induced apoptosis was accompanied by release of cytochrome c from the mitochondria. Aminoguanidine did not prevent glucose-induced myofibrillar degeneration, suggesting that formation of nitric oxide and/or advanced glycation end products play no major role. Taken together, these results suggest that in adult rat cardiac cells, palmitic acid induces apoptosis via de novo ceramide formation and activation of the apoptotic mitochondrial pathway. Conversely, glucose has no influence on adult cardiomyocyte apoptosis. However, both cell nutrients promote degeneration of myofibrils. Thus, gluco- and lipotoxicity may play a central role in the development of diabetic cardiomyopathy.

Animals↗

PubMed2003

High levels of palmitic acid lead to insulin resistance due to changes in the level of phosphorylation of the insulin receptor and insulin receptor substrate-1.

Insulin resistance is defined as the decrease in the glucose disposal in response to insulin by the target tissues. High concentrations of nonesterified fatty acids (NEFA) in plasma have been implicated with many insulin resistance states. We evaluated several aspects of the insulin resistance induced by palmitic acid in rats and found that after treatment with 0.09 g/kg of palmitic acid there is a delay in the curve of tolerance to glucose. We measured the changes in protein phosphorylation in samples from abdominus rectus muscle and there was a decrease of 64 and 75% in the levels of phosphorylation in tyrosine of the insulin receptor and insulin receptor substrate-1, respectively. This diminution in the tyrosine phosphorylation is consistent with a decrease in the main pathway known to be activated after insulin treatment, the mitogen activated protein kinases (MAPKs). If the animals were treated with inhibitors of PKC, like sphingosine, there was a prevention of the effect of palmitic acid determined at the level of tyrosine phosphorylation. According with this result, we found an increase in the phosphorylations in serine of the insulin receptor after the treatment with palmitate. These results suggest that PKC has a role as negative regulator (by phosphorylation in serine) of the insulin receptors activation in the insulin resistance induced by palmitic acid.

Animals↗

PubMed1990

Selective removal of retinoids and palmitic acid from microsomes by fatty acid binding protein and cellular retinol binding protein.

Studies were conducted to explore the effect of mouse liver cytosolic proteins enriched in fatty acid binding protein or cellular retinol binding protein on the removal of palmitic acid and retinoids from microsomal membranes. When the soluble proteins were incubated with mouse liver microsomes containing (14C)palmitic acid or (3H)retinoids, it was observed that fatty acid binding protein removed selectively the fatty acid and retinyl ester, whereas the retinol was mainly removed by cellular retinol binding protein.

Animals↗

PubMed1998

Definition of the specific roles of lysolecithin and palmitic acid in altering the susceptibility of dipalmitoylphosphatidylcholine bilayers to phospholipase A2.

Bilayers composed of phosphatidylcholine initially resist catalysis by phospholipase A2. However, after a latency period, they become susceptible when sufficient reaction products (lysolecithin and fatty acid) accumulate in the membrane. Temperature near the main bilayer phase transition and calcium concentration modulate the effectiveness of the reaction products. The purpose of this study was to examine the individual contributions of lysolecithin and palmitic acid to the susceptibility of dipalmitoylphosphatidylcholine vesicles and to rationalize the effects of temperature and calcium. Various fluorescent probes (Prodan, Laurdan, pyrene-labeled fatty acid, and dansyl-labeled phospholipid) were used to assess changes in the ability of the reaction products to perturb the bilayer and to affect the interactions with the enzyme. Un-ionized palmitic acid decreased bilayer polarity and perturbed the membrane surface exposing some of the Prodan to bulk water. Lysolecithin increased bilayer polarity and the rate of dipolar relaxation in response to the excited states of Laurdan and Prodan. A combination of the individual contributions of each product was observed when palmitic acid and lysolecithin were present together at low calcium, and the effects of lysolecithin dominated at high calcium. Palmitic acid, but not lysolecithin, promoted the binding of phospholipase A2 to the bilayer surface in the absence of calcium. Lysolecithin reduced the ability of fatty acid to enhance binding apparently by altering the structure of fatty acid domains in the membrane. Furthermore, increased temperature and ionization of the fatty acid tended to cause segregation of bound phospholipase A2 into domains poor in phospholipid content which presumably impeded bilayer hydrolysis. In contrast, un-ionized palmitic acid and lysolecithin promoted hydrolysis by augmenting a step distal to the adsorption of enzyme to the bilayer. This kinetic response to lysolecithin was calcium-dependent. A model accounting for these varied influences of the reaction products is presented.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1999

The effect of beta-chloro D-alanine and L-cycloserine on the serine, phosphorus and palmitic acid uptake and metabolism of Tetrahymena lipids.

The serine palmitoyltransferase inhibitors beta-chloro-D-alanine and L-cycloserine resulted in the uptake and metabolism of 3H-serine, 3H-palmitic acid and 32P significant alterations in the unicellular Tetrahymena pyriformis GL as compared to the untreated cells. In contrast with the higher eukariotic cells, by these treatments - except 5 mM L-cycloserine - the ceramide formation were not inhibited in Tetrahymena. L-cycloserine inhibited the conversion of phosphatidylserine (PS) to phosphatidyl-ethanolamine (PE) by decarboxylation, and the conversion of PE to phosphatidylcoline (PC) by methylation. The shorter L-cycloserine treatments caused lower, and the longer treatments higher label in glycerophospholipids. beta-chloro-D-alanine resulted in the glycerophospholids higher lipid precursor incorporation both in the shorter and longer treatments. Presumably beta-chloro-D-alanine treatments inhibit the transaminase activity, and the higher concentration (5 and 10 mM) proved to be toxic for Tetrahymena. We found differences between the metabolism of serine and palmitic acid labeled lipids in the beta-chloro-D-alanine and L-cycloserine treated groups. This phenomenon is probably due to a difference in the uptake of phospholipid head group component serine and hydrophobic tail precursor palmitic acid: the incorporation of palmitic acid in Tetrahymena is extremely quick, on the other hand, the uptake of serine is slower, a clear time dependence was measured.

Acyltransferases↗

PubMed1984

Acylation of bovine rhodopsin by [3H]palmitic acid.

Bovine retinas or preparations of rod outer segments incorporate [3H]palmitic acid into rhodopsin. The incorporation is both time- and temperature-dependent. The major product retains the chromatographic and electrophoretic properties of rhodopsin and remains photosensitive as demonstrated by alteration of its chromatographic behavior upon exposure to light. The incorporated radioactivity resists extraction with organic solvents and is not dissociated from the protein by detergents or under the denaturing conditions of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Radioactive free fatty acid can, however, be released by alkaline hydrolysis. Hydroxylamine treatment yields a mixture of the free fatty acid and the fatty acyl hydroxamate. These results demonstrate the formation of an ester bond between [3H]palmitic acid and rhodopsin. Cycloheximide fails to inhibit the incorporation. This finding along with the ability of rod outer segments to support the incorporation point to the acylation of rhodopsin as a late post-translational event.

Acylation↗

PubMed1977

Transaxial tomographic imaging of canine myocardium with 11C-palmitic acid.

Radiopharmaceuticals incorporated directly into the metabolic pathways in myocardium provide a useful means for evaluating such processes. Palmitic acid, a major physiologic substrate of myocardium, has a well-understood role in myocardial metabolism. Accordingly, 11C-palmitic acid was the substrate chosen for use in conjunction with positron emission transaxial tomography to obtain images of canine myocardium. This procedure provides high-contrast images of tranverse sections of the myocardium, with good target-to-nontarget ratios (in the image), over a period of 5 to 85 minutes. Clearance half-times for blood and myocardial tissue were found to be 4.8 and 330 min, respectively. In normal myocardium, images obtained with 11C-palmitic acid were those obtained with 13NH3 and 11CO-hemoglobin. In vivo images of hearts with myocardial infarcts showed a clear delineration of infarcts and normal tissue.

Ammonia↗

PubMed2001

Saturated FFAs, palmitic acid and stearic acid, induce apoptosis in human granulosa cells.

Obesity is associated with insulin resistance and some reproductive abnormalities. Circulating FFAs are often elevated in obese subjects and are also closely linked to insulin resistance. In this study, we demonstrated that saturated FFAs, such as palmitic acid and stearic acid, markedly suppressed the granulosa cell survival in a time- and dose-dependent manner. Polyunsaturated FFA, arachidonic acid, had no effect on the cell survival, even at supraphysiological concentrations. The suppressive effect of saturated FFAs on cell survival was caused by apoptosis, as evidenced by DNA ladder formation and annexin V-EGFP/propidium iodide staining of the cells. The apoptotic effects of palmitic acid and stearic acid were unrelated to the increase of ceramide generation or nitric oxide production and were also completely blocked by Triacsin C, an inhibitor of acylcoenzyme A synthetase. In addition, acylcoenzyme A, pamitoylcoenzyme A, and stearylcoenzyme A markedly suppressed granulosa cell survival, whereas arachidonoylcoenzyme A had no such effect, and this finding was consistent with the effect of the respective FFA form. Surprisingly, arachidonic acid instead showed a protective effect on palmitic acid- and stearic acid-induced cell apoptosis. A Western blot analysis showed the apoptosis of the granulosa cells induced by palmitic acid to be accompanied by the down-regulation of an apoptosis inhibitor, Bcl-2, and the up-regulation of an apoptosis effector, Bax. These results indicate that saturated FFAs induce apoptosis in human granulosa cells caused by the metabolism of the respective acylcoenzyme A form, and the actual composition of circulating FFAs may thus play a critical role in the apoptotic events of human granulosa cells. These effects of FFAs on granulosa cell survival may be a possible mechanism for reproductive abnormalities, such as amenorrhea, which is frequently observed in obese women.

Acyl Coenzyme A↗

PubMed1986

Palmitic acid oxidation and incorporation into triglyceride by needle liver biopsy specimens from control subjects and patients with alcoholic fatty liver disease.

A micro-technique was developed to measure fatty acid oxidation in vitro and to investigate its possible derangement in alcoholic fatty liver disease. Percutaneous liver biopsy specimens were obtained from nine control subjects and 28 alcoholic patients with mild to severe fatty liver. Fresh tissue (10-15 mg) was incubated at 37 degrees C for 90 min in a sealed reaction flask containing 1.92 mmol/l [1-14C]palmitic acid (1-2 microCi) and 1% essentially fatty acid free albumin in Krebs-Henseleit buffer, pH 7.4. Radiolabelled CO2 and perchloric acid-soluble ketone bodies were isolated and counted. CO2 production was markedly reduced in alcoholic patients with mild and severe fatty liver compared with controls. This depression was reversed by the addition of malate to the reaction flask but not by carnitine or coenzyme A. Ketone body production was similar in controls and patients with mild and severe fatty liver. After the incubation in vitro, the tissue was extracted with chloroform/methanol and the triglyceride fraction isolated by thin layer chromatography and counted for radioactivity. The rate of palmitic acid incorporation into triglyceride was higher in alcoholic patients, particularly those with severe fatty infiltration, compared with controls. It is suggested that alcoholic fatty liver is accompanied by a progressive reduction in palmitic acid oxidation with the major defect occurring in the tricarboxylic acid cycle. In contrast, the rate of palmitic acid esterification into triglyceride is enhanced.

Adult↗

PubMed1978

Esterification of palmitic acid in swine aortic homogenates.

The incorporation of [1-14C] palmitic acid into tissue lipids of the medial and intimal layers of swine aortic homogenates was investigated. The homogenates obtained were metabolically active as indicated by their ready incorporation of labeled palmitic acid into phospholipids, diglycerides and triglycerides in the presence of alpha-glycerophosphate in the incubation medium. Predominantly, labeling of phospholipids and especially of phosphatidylcholine was found when alpha-glycerophosphate or lysolecithin served as the fatty acid acceptor. Glycerol and monoolein did not serve as fatty acid acceptors. More than 98% of the radioactivity was recovered as the rephosphatidylcholine fraction at the level of 0.64 micromoles/ml of lysolecithin in the incubation medium.

Animals↗